B - Boot floor
Boot floor - The boot floor is not the piece of carpet in the boot, but the metal beneath. Many floors are home to the spare wheel and can trap water, so if you are buying second-hand, check very thoroughly that there's no water and no traces of rust.
In estates, make sure that there's no damage from carrying heavy loads. Also, always look underneath a car for signs of damage, in particular if it is an off-roader or has been used for towing. If the car is fitted with an underslung spare wheel, check it's there and in good condition.